Optical disk device

ABSTRACT

In an optical pickup driving mechanism using a stepping motor, a feeding operation of an optical pickup can be stabilized even in a broad operating temperature environment. In executing an optical axis correction feeding operation in response to an amount of lens shift of an objective lens of an optical pickup, a stepping motor controlling portion drives a stepping motor in a microstep drive mode to move a base of the optical pickup in a radial direction of an optical disk. At this time, a temperature sensor senses an in-equipment temperature, and a driving current supply time deciding portion sets a supply time width of a pulse driving current whose envelope is like a sinusoidal wave to a supply time width as a fixed value, which is longer than that at an ordinary time, or a supply time width, which is multiplied by a coefficient corresponding to the in-equipment temperature, to increase a current supply time of the driving current when the sensed in-equipment temperature is equal to or lower than a predetermined temperature.

THIS APPLICATION IS A U.S. NATIONAL PHASE APPLICATION OF PCTINTERNATIONAL APPLICATION PCT/JP2005/009685.

TECHNICAL FIELD

The present invention relates to an optical disk device having anoptical pickup for executing at least one of reading and writingoperations of information from and into a disk-type optical recordingmedium.

BACKGROUND ART

In case information is read/written from/into a disk-like opticalrecording medium (referred to as an “optical disk” hereinafter) such asCD, DVD, or the like in the optical disk device, a track on the opticaldisk must be scanned by moving an optical pickup in a radial direction(traverse direction) of the optical disk while rotating the optical diskby a spindle motor. As a feeding mechanism for the optical pickup in theradial direction of the disk, a stepping motor is often used recently.The stepping motor is suitable for the feeding mechanism for the opticalpickup because such motor can take a position at a fine rotation anglein response to an applied pulse train and also make a fast feed byfeeding the optical pickup as the object of drive in terms of a directdrive.

In the stepping motor, a rotor is rotated at a rotation angle that isproportional to the number of pulses applied as a driving current. FIG.15 is a view showing a revolving speed-torque characteristic of thestepping motor. In FIG. 15, an abscissa denotes a pulse rate of a drivepulse signal supplied as the driving current, i.e., a revolving speed ofthe stepping motor, and an ordinate a torque of the stepping motor inoperation. In a range (self-starting range) Ti below a pull-in torque,the stepping motor can start, stop, and reverse in synchronism with anapplied drive pulse signal. Also, in a range To in excess of a pull-outtorque, an out-of-step phenomenon occurs, so that the stepping motorcannot take a rotating action in synchronism with the drive pulsesignal. Also, in a range (through range) Ts between the pull-in torqueand the pull-out torque, the stepping motor can continue to rotate insynchronism with the drive pulse signal when such motor has already beenrotated, nevertheless an out-of-step phenomenon takes place and thestepping motor cannot make a normal rotation when such motor is startedfrom its stationary state. Since the stepping motor has theabove-mentioned characteristics, a design that is made based upon a loadtorque is absolutely essential to the stepping motor.

As the feeding operation of the optical pickup, there are an operationfor performing intermittently a feed of about several tens μm in readingor writing the information from or into the optical disk (referred to asan “optical axis correction feeding operation” hereinafter) and a seekoperation for performing a feed at a high speed toward the designatedtrack over a long distance. In general, a full step drive (two-phaseexcitation drive) is executed in the seek operation that needs a fastmovement of the optical pickup, while a microstep drive is executed inthe optical axis correction feeding operation that needs a fine feedcontrol of about several tens μm.

In the optical axis correction feeding operation, in order to scan thetrack on the optical disk, an objective lens of the optical pickup movesin the traverse direction following to the track that is recordedspirally or concentrically on the optical disk. At this time, a trackingactuator of the optical pickup executes position control of theobjective lens with respect to the track of the optical disk. Since amovable range of the tracking actuator of the optical pickup is limited,the stepping motor is controlled in such a manner that, when theobjective lens is shifted from a center of a base of the optical pickupby a predetermined amount, the base of the optical pickup is moved inabout several tens μm in the traverse direction to cancel a shiftedamount.

In the optical axis correction feeding operation, the stepping motorexecutes the feeding operation in the microstep drive. As shown in FIG.16, in the microstep drive, a driving current like a sinusoidal wave isapplied to respective terminals of the stepping motor to rotate themotor smoothly at a rotation angle smaller than a step angle peculiar toeach motor. The microstep drive can make an infinitesimal feed of theoptical pickup while suppressing generation of a vibration.

In the stepping motor, when the microstep drive is carried out in theform of continuous current supply, a consumption power is increased andalso generation of heat is increased. Thus, such a problem arose thatthe life of parts is shortened or an operating temperature limit of thedrive must be restricted. Therefore, the optical disk device forcontrolling the drive of the stepping motor by applying a drivingcurrent for the microstep drive only in predetermined time (severalmsec) is known (see Patent Literature 1, for example).

The optical axis correction feeding operation is continued during thereading or writing operation of the information from or into the opticaldisk, while the stepping motor is controlled such that the steppingmotor is driven to cancel a shifted amount when a predetermined shift ofthe objective lens is generated. In other words, an operation of drivingthe stepping motor is repeated every time when a lens shift of theobjective lens is generated, so that the information can be readcorrectly by driving intermittently the stepping motor.

Patent Literature 1: JP-A-10-149639

Disclosure of the Invention

Problems that the Invention is to Solve

However, when an operating temperature range of the optical disk deviceis broad in an onboard application, or the like, a mechanical loadcharacteristic is changed following upon a change of temperature.Therefore, even in the device that operates normally at an ordinarytemperature, the load was increased at a low temperature due to theinfluence of a grease viscosity, and in some cases the stepping motorproduced an out-of-step phenomenon and was unable to take a normaloperation.

For this reason, the measure should be taken, e.g., an expensive greasethat has a less variation in the temperature characteristic should beemployed, a performance guarantee temperature range should be limited inoperation, or the like. Therefore, it is difficult to accomplish thehigh-performance inexpensive device whose operating temperature range isboard. In particular, in the case of the onboard optical disk deviceemployed as the onboard audio-visual equipment, the navigation system,or the like, it is feared that the above phenomenon becomes actualbecause such equipment is often used in the low temperature environment.

The present invention has been made in view of the above circumstances,and it is an object of the present invention to provide an optical diskdevice capable of stabilizing a feeding operation of an optical pickupeven in a broad operating temperature environment in an optical pickupdriving mechanism using a stepping motor.

Means for Solving the Problems

First, an optical disk device of the present invention, includes anoptical pickup for reading information recorded on an optical disk; astepping motor for moving the optical pickup in a radial direction ofthe optical disk; a driving current supplying unit for supplying adriving current to drive the stepping motor, and executing a microstepdrive; a temperature sensing unit for sensing an ambient temperature ofthe optical pickup; and a drive controlling unit for executing drivecontrol of the stepping motor by changing the driving current applied inthe microstep drive in response to the sensed ambient temperature.

Accordingly, the driving current of the stepping motor in executing themicrostep drive is changed in response to the ambient temperature.Therefore, the stepping motor can be driven by the appropriate torque inanswer to the load that changes depending on the temperature, and alsothe feeding operation of the optical pickup can be stabilized in thebroad operating temperature environment.

Also, second, as one mode of the present invention, the driving currentsupplying unit supplies an intermittent driving current at apredetermined time width to the stepping motor in executing themicrostep drive, and the drive controlling unit changes a supply timewidth of the driving current in response to the ambient temperature.

Accordingly, the supply time width of the driving current is changed inresponse to the ambient temperature. Therefore, the stepping motor canbe driven by the appropriate torque that agrees with the load thatchanges depending on the temperature, and also the optical disk devicecan be used in the broad operating temperature environment by preventingoccurrence of the defective operation in reading/writing theinformation.

Also, third, as one mode of the present invention, the drive controllingunit changes the supply time width of the driving current into anincreased value when the ambient temperature is equal to or lower than apredetermined temperature.

Accordingly, the supply time width of the driving current is increasedwhen the ambient temperature is equal to or lower than a predeterminedtemperature. Therefore, the stepping motor can be driven by theappropriate torque in answer to the load that is increased in a lowtemperature range.

Also, fourth, the optical disk device of the present invention, furtherincludes a temperature coefficient translation table for storing atemperature coefficient corresponding to the ambient temperature;wherein the drive controlling unit calculates the temperaturecoefficient corresponding to the ambient temperature by using thetemperature coefficient translation table, and decides the supply timewidth of the driving current.

Therefore, the appropriate supply time width of the driving current canbe set by using the temperature coefficient that corresponds to theambient temperature, and also the stepping motor can be driven by theappropriate torque in compliance with the ambient temperature.

Also, fifth, an optical disk device of the present invention, includesan optical pickup for reading information recorded on an optical disk; astepping motor for moving the optical pickup in a radial direction ofthe optical disk; a driving current supplying unit for supplying adriving current to drive the stepping motor, and executing selectively afull step drive and a microstep drive; a full step drive deciding unitfor deciding whether or not an operation taken when the optical pickupis moved in the full step drive is normally ended; and a drivecontrolling unit for executing drive control of the stepping motor bychanging the driving current applied in the microstep drive in responseto a decision result.

Accordingly, the driving current applied in the microstep drive of thestepping motor is changed in response to the decision result indicatingwhether or not the optical pickup moving operation in the full stepdrive has been normally ended. Therefore, the stepping motor can bedriven by the torque that is appropriate for the load that changesdepending on the temperature, and also the feeding operation of theoptical pickup can be stabilized in the broad operating temperatureenvironment.

Also, sixth, the optical disk device of the present invention furtherincludes a driving current changing unit for changing the drivingcurrent applied in the full step drive.

Therefore, it is possible to decide whether or not the optical pickupmoving operation will be normally ended, by changing the driving currentapplied in the full step drive.

Also, seventh, as one mode of the present invention, the driving currentchanging unit changes stepwise a current amplitude of the drivingcurrent applied in the full step drive.

Therefore, it is possible to decide whether or not the optical pickupmoving operation will be normally ended, in response to the currentamplitude value when the current amplitude of the driving currentapplied in the full step drive is changed stepwise.

Also, eighth, the optical disk device of the present invention furtherincludes a normal driving current amplitude deciding unit for deciding acurrent amplitude value of the driving current by which a feedingoperation in the full step drive is normally executed; and wherein thedriving current supplying unit supplies an intermittent driving currentat a predetermined time width to the stepping motor in executing themicrostep drive, and the drive controlling unit changes a supply timewidth of the driving current in response to the current amplitude widthof the driving current.

Accordingly, the supply time width of the driving current applied in themicrostep drive is changed in response to the current amplitude value ofthe driving current by which the feeding operation in the full stepdrive can be normally executed. Therefore, the stepping motor can bedriven by the appropriate torque that agrees with the load that changesdepending on the temperature, and also the optical disk device can beused in the broad operating temperature environment by preventingoccurrence of the defective operation in reading/writing theinformation.

Also, ninth, the optical disk device of the present invention furtherincludes an optical pickup position sensing unit for sensing whether ornot a movement of the optical pickup to a predetermined position of aninner circumference of the optical disk is completed; and a movingcomplete current amplitude deciding unit for deciding a currentamplitude value of the driving current such that the movement of theoptical pickup to the predetermined position of the inner circumferenceof the optical disk is completed within a predetermined time in the fullstep drive; wherein the driving current supplying unit supplies anintermittent driving current at a predetermined time width to thestepping motor in executing the microstep drive, and the drivecontrolling unit changes a supply time width of the driving current inresponse to the current amplitude value of the driving current.

Accordingly, the supply time width of the driving current applied in themicrostep drive is changed in response to the current amplitude value ofthe driving current decided in such a manner that the movement of theoptical pickup to the predetermined position of the inner circumferenceis completed within the predetermined time in the full step drive.Therefore, the stepping motor can be driven by the appropriate torquethat agrees with the load that changes depending on the temperature, andalso the optical disk device can be used in the broad operatingtemperature environment by preventing occurrence of the defectiveoperation in reading/writing the information.

Also, tenth, as one mode of the present invention, the drive controllingunit changes the supply time width of the driving current into anincreased value when the current amplitude value is equal to or greaterthan a predetermined value.

Accordingly, the supply time width of the driving current is increasedwhen the current amplitude value of the driving current decided suchthat the feeding operation in the full step drive can be normallyexecuted is equal to or smaller than a predetermined value. Therefore,the stepping motor can be driven by the appropriate torque in answer tothe load that is increased in the low temperature range, or the like,for example.

Also, eleventh, the optical disk device of the present invention furtherincludes an optical pickup position sensing unit for sensing whether ornot a movement of the optical pickup to a predetermined position of aninner circumference of the optical disk is completed; and a moving timedeciding unit for deciding a moving time required until the opticalpickup is moved to the predetermined position of the inner circumferencein the full step drive; wherein the driving current supplying unitsupplies an intermittent driving current at a predetermined time widthto the stepping motor in executing the microstep drive, and the drivecontrolling unit changes a supply time width of the driving current inresponse to the moving time of the optical pickup.

Accordingly, the supply time width of the driving current applied in themicrostep drive is changed in response to the moving time required untilthe optical pickup is moved to the predetermined position of the innercircumference in the full step drive. Therefore, the stepping motor canbe driven by the appropriate torque that agrees with the load thatchanges depending on the temperature, and also the optical disk devicecan be used in the broad operating temperature environment by preventingoccurrence of the defective operation in reading/writing theinformation.

Also, twelfth, as one mode of the present invention, the drivecontrolling unit changes the supply time width of the driving currentinto an increased value when the moving time is equal to or longer thana predetermined value.

Accordingly, the supply time width of the driving current is increasedwhen the moving time required until the optical pickup is moved to thepredetermined position of the inner circumference in the full step driveis equal to or longer than the predetermined value. Therefore, thestepping motor can be driven by the appropriate torque in answer to theload that is increased in the low temperature range, or the like, forexample.

Also, thirteenth, an optical disk device of the present invention,includes an optical pickup for reading information recorded on anoptical disk; a stepping motor for moving the optical pickup in a radialdirection of the optical disk; a driving current supplying unit forsupplying a driving current to drive the stepping motor, executingselectively a full step drive and a microstep drive, and supplying anintermittent driving current at a predetermined time width to thestepping motor in executing the microstep drive; a driving currentchanging unit for changing a pulse rate of the driving current appliedin the full step drive; a full step drive deciding unit for decidingwhether or not an operation taken when the optical pickup is moved inthe full step drive is normally ended; and a drive controlling unit forexecuting drive control of the stepping motor by changing a supply timewidth of the driving current applied in the microstep drive in responseto a decision result.

Accordingly, the driving current applied in the microstep drive of thestepping motor is changed in response to the decision result indicatingwhether or not the optical pickup moving operation in the full stepdrive has been completed normally. Therefore, the stepping motor can bedriven by the torque that is appropriate for the load that changesdepending on the temperature, and also the feeding operation of theoptical pickup can be stabilized in the broad operating temperatureenvironment.

Also, fourteenth, as one mode of the present invention, the drivingcurrent changing unit changes stepwise the pulse rate of the drivingcurrent in executing the full step drive.

Therefore, it is possible to decide whether or not the optical pickupmoving operation will be normally ended, in response to a pulse ratevalue when the pulse rate of the driving current applied in the fullstep drive is changed stepwise.

Also, fifteenth, the optical disk device of the present inventionfurther includes a normal drive pulse rate deciding unit for decidingthe pulse rate of the driving current such that a feeding operation isnormally executed in the full step drive; and wherein the drivecontrolling unit changes the supply time width of the driving current inresponse to the pulse rate of the driving current.

Accordingly, the supply time width of the driving current applied in themicrostep drive is changed in response to the pulse rate of the drivingcurrent by which the feeding operation in the full step drive can benormally executed. Therefore, the stepping motor can be driven by theappropriate torque that agrees with the load that changes depending onthe temperature, and also the optical disk device can be used in thebroad operating temperature environment by preventing occurrence of thedefective operation in reading/writing the information.

Also, sixteenth, the optical disk device of the present inventionfurther includes an optical pickup position sensing unit for sensingwhether or not a movement of the optical pickup to a predeterminedposition of an inner circumference of the optical disk is completed; anda moving complete pulse rate deciding unit for deciding the pulse rateof the driving current such that the movement of the optical pickup tothe predetermined position of the inner circumference of the opticaldisk is completed within a predetermined time in the full step drive;wherein the drive controlling unit changes the supply time width of thedriving current in response to the pulse rate of the driving current.

Accordingly, the supply time width of the driving current applied in themicrostep drive is changed in response to the pulse rate of the drivingcurrent decided in such a manner that the movement of the optical pickupto the predetermined position of the inner circumference is completed inthe full step drive within the predetermined time. Therefore, thestepping motor can be driven by the appropriate torque that agrees withthe load that changes depending on the temperature, and also the opticaldisk device can be used in the broad operating temperature environmentby preventing occurrence of the defective operation in reading/writingthe information.

Also, seventeenth, as one mode of the present invention, the drivecontrolling unit changes the supply time width of the driving currentinto an increased value when the pulse rate is equal to or smaller thana predetermined value.

Accordingly, the supply time width of the driving current is increasedwhen the pulse rate of the driving current decided such that the feedingoperation in the full step drive can be normally executed is equal to orsmaller than a predetermined value. Therefore, the stepping motor can bedriven by the appropriate torque in answer to the load that is increasedin the low temperature range, or the like, for example.

Also, eighteenth, the optical disk device of the present inventionfurther includes an optical pickup position sensing unit for sensingwhether or not a movement of the optical pickup to a predeterminedposition of an inner circumference of the optical disk is completed; anda moving time deciding unit for deciding a moving time required untilthe optical pickup is moved to the predetermined position of the innercircumference in the full step drive; wherein the drive controlling unitchanges the supply time width of the driving current in response to themoving time of the optical pickup.

Accordingly, the supply time width of the driving current applied in themicrostep drive is changed in response to the moving time required untilthe optical pickup is moved to the predetermined position of the innercircumference in the full step drive. Therefore, the stepping motor canbe driven by the appropriate torque that agrees with the load thatchanges depending on the temperature, and also the optical disk devicecan be used in the broad operating temperature environment by preventingoccurrence of the defective operation in reading/writing theinformation.

Also, nineteenth, as one mode of the present invention, the drivecontrolling unit changes the supply time width of the driving currentinto an increased value when the moving time is equal to or longer thana predetermined value.

Accordingly, the supply time width of the driving current is increasedwhen the moving time required until the optical pickup is moved to thepredetermined position of the inner circumference in the full step driveis equal to or longer than the predetermined value. Therefore, thestepping motor can be driven by the appropriate torque in answer to theload that is increased in the low temperature range, or the like, forexample.

Also, twentieth, as one mode of the present invention, a decisionregarding a drive of the optical pickup in the full step drive is madeduring an inner circumferential feeding operation that is applied toinitialize a position of the optical pickup immediately after theoptical disk device is started.

Therefore, the driving current applied in the microstep drive can becontrolled by making the decision regarding the drive of the opticalpickup in the full step drive, e.g., whether the operation taken whenthe optical pickup is moved in the full step drive upon initializing aposition of the optical pickup immediately after the optical disk deviceis started is normally ended or not, or the like.

Also, twenty-first, an onboard equipment of the present inventionincludes an optical disk device.

In particular, in the onboard equipment used in the broad temperaturerange such as the low temperature environment, and the like, when theabove optical disk device is applied to the equipment, the feedingoperation of the optical pickup can be stabilized irrespective of theambient temperature and also occurrence of the operational failure canbe prevented.

Advantages of the Invention

According to the present invention, an optical disk device capable ofstabilizing a feeding operation of an optical pickup even in a broadoperating temperature environment in an optical pickup driving mechanismusing a stepping motor can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 A block diagram showing a schematic configuration of an opticaldisk device according to first and second embodiments of the presentinvention.

FIG. 2 A flowchart showing procedures of a current supply time settingoperation in a microstep drive mode in the first embodiment.

FIG. 3 Views showing a driving current in the microstep drive mode of astepping motor in the first embodiment respectively.

FIG. 4 A flowchart showing procedures of a current supply time settingoperation in a microstep drive mode in the second embodiment.

FIG. 5 Views showing a driving current in the microstep drive mode of astepping motor in the second embodiment respectively.

FIG. 6 A block diagram showing a schematic configuration of an opticaldisk device according to a third embodiment of the present invention.

FIG. 7 A flowchart showing procedures of a current supply time settingoperation in a microstep drive mode in the third embodiment.

FIG. 8 A view showing a full step drive current of a stepping motor ininner circumference seek operation in the third embodiment.

FIG. 9 Views showing a driving current in the microstep drive mode of astepping motor in the third embodiment respectively.

FIG. 10 A block diagram showing a schematic configuration of an opticaldisk device according to a fourth embodiment of the present invention.

FIG. 11 A flowchart showing procedures of a current supply time settingoperation in a microstep drive mode in the fourth embodiment.

FIG. 12 Views showing a relationship between a pulse rate of a drivingcurrent of a stepping motor and a torque in the fourth embodimentrespectively.

FIG. 13 A view showing a full step drive current of a stepping motor ininner circumference seek operation in the fourth embodiment.

FIG. 14 A view showing a driving current of a stepping motor in amicrostep drive mode in the fourth embodiment.

FIG. 15 A view showing a revolving speed-torque characteristic of thestepping motor.

FIG. 16 Views showing a driving current in a microstep drive mode of thestepping motor respectively.

DESCRIPTION OF REFERENCE NUMERALS AND SIGNS

-   1 optical disk-   2 spindle motor-   3 optical pickup-   4 stepping motor-   5 objective lens-   6 actuator-   7 base-   8 guide shaft-   9 revolving shaft-   10 feed screw-   11 feed screw holder-   12 spindle motor driving portion-   13 optical pickup driving portion-   14 stepping motor driving portion-   15 head amplifier-   16 signal processing portion-   17 temperature sensor-   18 inner circumference switch-   20 controller-   21 spindle motor controlling portion-   22 optical pickup controlling portion-   23 stepping motor controlling portion-   24 lens shift amount sensing portion-   31 driving current supply time deciding portion-   32 temperature-current supply time translation table-   33 driving current profile generating portion-   41 timer-   42 inner circumferential position sensing portion-   43 moving time deciding portion-   50 controller-   51 stepping motor controlling portion-   52 full step drive controlling portion-   53 microstep drive controlling portion-   54 full step driving current amplitude-current supply time    translation table-   55 full step driving current amplitude deciding portion-   56 full step driving current profile generating portion-   57 microstep driving current supply time deciding portion-   58 microstep driving current profile generating portion-   60 controller-   61 stepping motor controlling portion-   62 full step drive controlling portion-   63 microstep drive controlling portion-   64 full step driving current pulse rate-current supply time    translation table-   65 full step driving current pulse rate deciding portion-   66 full step driving current profile generating portion-   67 microstep driving current supply time deciding portion-   68 microstep driving current profile generating portion    Best Mode for Carrying Out the Invention

FIG. 1 is a block diagram showing a schematic configuration of anoptical disk device according to first and second embodiments of thepresent invention.

In the present embodiment, a configurative example of the optical diskdevice that executes optically at least one of reading and writingoperations of the information by using the optical disk such as CD, DVD,or the like as the recording medium is shown. This optical disk deviceis suitable to the onboard equipment such as a CD player, a DVD player,a navigation system, or the like.

The optical disk device is constructed to have a spindle motor 2 forrotating while holding an optical disk 1, an optical pickup 3 forirradiating a laser beam to the optical disk 1 to read and write theinformation, and a stepping motor 4 for moving the optical pickup 3 in aradial direction of the optical disk 1. A spiral track is formed on arecording face of the optical disk 1 from an inner circumference to anouter circumference (or from an outer circumference to an innercircumference), and various information are recorded on the track.

The optical pickup 3 has a light emitting laser diode as a light source,a photo detector as a light receiving portion, and various opticalelement parts, and is constructed to have an objective lens 5 forfocusing a recording/producing laser beam on the recording face of theoptical disk 1, an actuator 6 for driving the objective lens 5, and abase 7 to which the above constituent parts are fitted. A pair of guideshafts 8 extended in the radial direction of the optical disk 1 areinserted into the base 7 of the optical pickup 3 such that the base 7can be slid along the guide shafts 8. The guide shafts 8 have functionsof supporting the optical pickup 3 and guiding the optical pickup 3 whenthe optical pickup 3 is moved toward the inner or outer circumference ofthe optical disk 1 in its radial direction.

A revolving shaft 9 of the stepping motor 4 is extended in parallel withthe guide shafts 8. A feed screw 10 is formed on the revolving shaft 9,and a feed screw holder 11 fixed to the base 7 of the optical pickup 3engages with the feed screw 10. According to this configuration, arotary motion of the stepping motor 4 is converted into a straight-linemotion when the stepping motor 4 is rotated/driven, so that the base 7of the optical pickup 3 is moved in the radial direction of the opticaldisk 1. In this example in FIG. 1, a configuration having two guideshafts and one feed screw is illustrated, but a configuration in whichthe feed screw is also used as the guide shafts may be employed.

Also, the optical disk device includes a spindle motor driving portion12 for driving the spindle motor 2, an optical pickup driving portion 13for driving the actuator 6 of the optical pickup 3, and a stepping motordriving portion 14 for driving the stepping motor 4. Also, the opticaldisk device includes a head amplifier 15 for amplifying a read signalread by the optical pickup 3, a signal processing portion 16 forprocessing an output signal from the head amplifier 15, and atemperature sensor 17 for sensing an in-equipment temperature as anambient temperature of the optical pickup 3.

Also, the optical disk device includes a controller 20 having aprocessor for controlling respective portions. The controller 20 isconstructed to have a spindle motor controlling portion 21, an opticalpickup controlling portion 22, a stepping motor controlling portion 23,and a lens shift amount sensing portion 24. The stepping motorcontrolling portion 23 has a driving current supply time decidingportion 31, a temperature-current supply time translation table 32, anda driving current profile generating portion 33.

In the above configuration, the spindle motor driving portion 12generates a driving motor to rotate/drive the spindle motor 2, and thespindle motor controlling portion 21 controls the driving current outputfrom the spindle motor driving portion 12 to keep the spindle motor 2 ata predetermined number of revolutions. The optical pickup 3 reads/writesthe information from/into the optical disk 1 rotated by the spindlemotor 2 while moving from an inner circumference to an outercircumference (or from an outer circumference to an inner circumference)of the optical disk 1 in its radial direction. At this time, a laserbeam is focused on a pit on the track of the optical disk 1 by theobjective lens 5 of the optical pickup 3.

The actuator 6 of the optical pickup 3 has a focus actuator for movingthe objective lens 5 in the focusing direction (normal direction to therecording face of the optical disk 1), and a tracking actuator formoving the objective lens 5 in the tracking direction (directionintersecting orthogonally with the track on the recording face of theoptical disk 1). A focusing of a laser beam is conducted by the focusactuator, and a correction of displacement from the track on the opticaldisk 1 is conducted by the tracking actuator.

The head amplifier 15 amplifies signals read by the optical pickup 3,and generates RF signals of a focus error (FE) signal, a tracking error(TE) signal, and a read signal to output them. The signal processingportion 16 executes demodulation and error correction processes of theRF signals amplified by the head amplifier 15, and outputs the processedsignals to the controller 20. The optical pickup driving portion 13generates a driving current to drive the actuator 6 of the opticalpickup 3.

The optical pickup controlling portion 22 in the controller 20 outputs acontrol signal, which controls a position of the objective lens 5 basedon the focus error signal and the tracking error signal being outputfrom the head amplifier 15, to the optical pickup driving portion 13.The focus actuator and the tracking actuator of the optical pickup 3 aredriven by the optical pickup driving portion 13 based on this controlsignal. The lens shift amount sensing portion 24 senses an amount ofshift at which the objective lens 5 shifts from a center of the base 7of the optical pickup 3.

The feed screw 10 acts as an output shaft of the stepping motor 4. Whenthe stepping motor 4 rotates, its rotating power is transmitted from thefeed screw 10 via the feed screw holder 11, so that the base 7 of theoptical pickup 3 is moved in the radial direction of the optical disk 1.Normally, in the optical disk device, a seek operation to read theinformation about inner and outer circumferences of the optical diskmust be executed frequently. Therefore, the grease is smeared on thefeed screw 10 and the feed screw holder 11 to secure a wear resistanceof the sliding portions. The stepping motor 4 is rotated by the drivingcurrent from the stepping motor driving portion 14. The stepping motorcontrolling portion 23 controls the driving current output from thestepping motor driving portion 14. A sensing signal of the in-equipmenttemperature of the optical disk device sensed with the temperaturesensor 17 is input into the driving current supply time deciding portion31 of the stepping motor controlling portion 23.

The driving current supply time deciding portion 31 decides a drivingcurrent supply time in the microstep drive, based on this temperaturesensing signal and an output of the temperature-current supply timetranslation table 32. The driving current profile generating portion 33generates a driving current profile, which is used for the microstepdrive and whose envelope is sinusoidal, in response to a supply timewidth decided by the driving current supply time deciding portion 31 andoutputs it to the stepping motor driving portion 14.

Next, an operation of the optical disk device constructed as above willbe explained hereunder. Since operations of reading/writing theinformation from/into the optical disk 1 are similar to those of thecommon optical disk device, their detailed explanation will be omittedherein. A controlling operation of the stepping motor 4 as an operationpeculiar to the present embodiment in the optical axis correctionfeeding operation in the microstep drive will be explained herein.

Upon reading/writing the information after the optical disk device isstarted or after the seek operation is finished, the optical axiscorrection feeding operation is executed. When the optical pickup 3starts reading of information by turning ON the tracking servo, theactuator 6 is controlled such that the objective lens 5 is moved in theradial direction (from an inner circumference to an outer circumferenceor from an outer circumference to an inner circumference) to follow upthe track of the optical disk 1. A lens shift, i.e., the objective lens5 is shifted gradually from the center of the base 7 of the opticalpickup 3, is generated while the information is being read or written.After a predetermined amount of lens shift is generated, a drivingcurrent used in the microstep drive is applied from the stepping motordriving portion 14 to move the stepping motor 4 by a predeterminedamount. The base 7 of the optical pickup 3 is moved in the microstepdrive of the stepping motor 4 to cancel the lens shift, and then thestepping motor 4 is stopped. The above operations are executedsuccessively until the objective lens 5 completes the reading of thefinal address of the optical disk 1 or the final address of informationreading interval designated by the operator, and then the optical axiscorrection feeding operation is finished when the objective lens 5reaches the address.

In the present embodiment, driving current control applied to drive thestepping motor 4 during the optical axis correction feeding operation inthe microstep drive mode will be carried out as follows. Two examples offirst and second embodiments will be given herein.

FIG. 2 is a flowchart showing procedures of a current supply timesetting operation in the microstep drive mode in the first embodiment.The first embodiment gives an example where, in response to a sensingsignal of the in-equipment temperature output from the temperaturesensor 17, a current supply time is switched to be prolonged when thein-equipment temperature is lower than a predetermined temperature.

When a driving current supply time setting operation in the microstepdrive mode is started (step S21), an in-equipment temperature θf of theoptical disk device is measured as an ambient temperature of the opticalpickup 3 with the temperature sensor 17 (step S22). Then, the drivingcurrent supply time deciding portion 31 compares the in-equipmenttemperature θf sensed with the temperature sensor 17 with apredetermined reference temperature θc (step S23).

In step S23, if it is decided that the in-equipment temperature θf islower than the reference temperature θc, the driving current supply timedeciding portion 31 considers that the optical disk device is being usedin a low temperature environment. Then, the driving current supply timedeciding portion 31 sets a supply time width of the driving current inthe microstep drive to a current supply time tL as a fixed value that islonger than a current supply time tc at an ordinary temperature (stepS24), and then ends the driving current supply time setting operation(step S25).

In contrast, in step S23, if it is decided that the in-equipmenttemperature θf is higher than the reference temperature θc, the drivingcurrent supply time deciding portion 31 sets the supply time width ofthe driving current in the microstep drive to the current supply time tcat an ordinary temperature (step S26), and then ends the driving currentsupply time setting operation (step S25).

FIG. 3 are views showing the driving current in the microstep drive modeof the stepping motor in the first embodiment respectively. When thein-equipment temperature θf is higher than the reference temperature θc,the supply time width of the driving current is set to the currentsupply time tc at an ordinary temperature, as shown in FIG. 3( a), andthe pulse driving current whose envelope is like a sinusoidal wave issupplied from the stepping motor driving portion 14. When thein-equipment temperature θf is lower than the reference temperature θc,the supply time width of the driving current is set to a current supplytime tL at a low temperature, as shown in FIG. 3( b), and the drivingcurrent is switched to prolong the supply time width.

In this manner, in the first embodiment, the supply time width of thedriving current in the microstep drive mode is changed in response tothe in-equipment temperature of the optical disk device sensed with thetemperature sensor. When the in-equipment temperature is lower than apredetermined temperature, the supply time width of the driving currentis set longer than that at an ordinary temperature. As a result, inexecuting the optical axis correction feeding operation when the lensshift of the objective lens exceeds a predetermined amount, the steppingmotor can be driven by a proper torque in the low temperatureenvironment and also the optical disk device can be operated stably.

FIG. 4 is a flowchart showing procedures of the current supply timesetting operation in the microstep drive mode in the second embodiment.The second embodiment gives an example where a temperature coefficientis calculated by using the temperature-current supply time translationtable 32 in response to a sensing signal of the in-equipment temperatureoutput from the temperature sensor 17 and also a current supply time isset.

When the driving current supply time setting operation in the microstepdrive mode is started (step S31), the in-equipment temperature θf theoptical disk device is measured as an ambient temperature of the opticalpickup 3 with the temperature sensor 17 (step S32). Then, the drivingcurrent supply time deciding portion 31 calculates a temperaturedifference θd between the in-equipment temperature θf sensed with thetemperature sensor 17 and a predetermined reference temperature θc (stepS33). Then, the driving current supply time deciding portion 31 outputsa temperature coefficient k based on the temperature-current supply timetranslation table 32 to decide a supply time width of the drivingcurrent corresponding to the temperature difference θd (step S34). Then,the driving current supply time deciding portion 31 sets a currentsupply time tf, which is derived by multiplying the current supply timetc as the reference at an ordinary temperature by the temperaturecoefficient k, to the supply time width of the driving current (stepS35), and then ends the driving current supply time setting operation(step S36).

FIG. 5 are views showing the driving current in the microstep drive modeof the stepping motor in the second embodiment respectively. When thein-equipment temperature θf is higher than the reference temperature θc,i.e., when the temperature difference θd is positive, e.g., thetemperature coefficient k=1 is set, the supply time width of the drivingcurrent is set to the current supply time t at an ordinary temperature,as shown in FIG. 5( a), and then the pulse driving current whoseenvelope is like a sinusoidal wave is supplied from the stepping motordriving portion 14. When the in-equipment temperature θf is lower thanthe reference temperature θc, i.e., when the temperature difference θdis negative, e.g., the temperature coefficient k>1 is set, the supplytime width of the driving current is set to a current supply timetf=k×tc, as shown in FIG. 5( b), and then the driving current isswitched to extend the supply time width. At this time, the supply timewidth of the driving current can be changed continuously or stepwise inanswer to the in-equipment temperature θf.

In this manner, in the second embodiment, since the temperaturecoefficient is calculated based on the in-equipment temperature of theoptical disk device sensed with the temperature sensor and then thecurrent supply time responding to the temperature difference from thereference temperature is set by multiplying the current supply time asthe reference by the temperature coefficient, the supply time width ofthe driving current in the microstep drive mode can be changed. At thistime, when the in-equipment temperature is low, the current supply timeis set to extend the supply time width of the driving current. As aresult, in executing the optical axis correction feeding operation whenthe lens shift of the objective lens exceeds a predetermined amount, thestepping motor can driven by the adequate torque in the broadtemperature environment and also the optical disk device can be operatedstably.

As explained above, according to the first and second embodiments, inthe case where, upon executing the optical axis correction feedingoperation in the microstep drive, the driving current is suppliedintermittently every predetermined time width by suppressing aconsumption current to reduce an amount of heat generation, thein-equipment temperature is sensed with the temperature sensor and thesupply time width of the driving current is set in response to thesensed in-equipment temperature. Therefore, the stepping motor candriven by the torque that agrees with the load torque in use. As aresult, the feeding operation of the optical pickup using the opticalpickup driving mechanism using the stepping motor can be stabilized inthe broad operating temperature environment.

FIG. 6 is a block diagram showing a schematic configuration of anoptical disk device according to a third embodiment of the presentinvention. Here, the same reference symbols are affixed to the sameconstituent elements as those in the above first and second embodiments,and their explanation will be omitted herein.

The optical disk 1 in the third embodiment includes an innercircumference switch 18 that is turned ON when the optical pickup 3arrives at a predetermined position of the inner circumferential portionof the optical disk 1.

Also, the optical disk device includes a controller 50 having aprocessor for controlling respective portions. The controller 50 has thespindle motor controlling portion 21, the optical pickup controllingportion 22, the lens shift amount sensing portion 24, a timer 41, aninner circumferential position sensing portion 42, a moving timedeciding portion 43, and a stepping motor controlling portion 51. Thestepping motor controlling portion 51 is constructed to have a full stepdrive controlling portion 52, a microstep drive controlling portion 53,and a full step driving current amplitude-current supply timetranslation table 54. The full step drive controlling portion 52 has afull step driving current amplitude deciding portion 55 and a full stepdriving current profile generating portion 56. The microstep drivecontrolling portion 53 has a microstep driving current supply timedeciding portion 57 and a microstep driving current profile generatingportion 58.

In the above configuration, the optical pickup controlling portion 22 inthe controller 50 outputs a control signal, which is applied to controla position of the objective lens 5 based on the focus error signal andthe tracking error signal output from the head amplifier 15, to theoptical pickup driving portion 13. The focus actuator and the trackingactuator of the optical pickup 3 are driven by the optical pickupdriving portion 13 based on this control signal. The lens shift amountsensing portion 24 senses an amount of shift at which the objective lens5 shifts from the center of the base 7 of the optical pickup 3.

The feed screw 10 serves as the output shaft of the stepping motor 4.The rotating power of the stepping motor 4, when it rotates, istransmitted from the feed screw 10 via the feed screw holder 11, so thatthe base 7 of the optical pickup 3 is moved in the radial direction ofthe optical disk 1. Normally, in the optical disk device, the seekoperation to read the information about inner and outer circumferencesof the optical disk must be executed frequently. Therefore, the greaseis smeared on the feed screw 10 and the feed screw holder 11 to secure awear resistance of the sliding portions.

The stepping motor 4 is rotated by the driving current from the steppingmotor driving portion 14. The stepping motor controlling portion 51 inthe controller 50 controls the driving current output from the steppingmotor driving portion 14, and can switch the full step drive and themicrostep drive in the full step drive controlling portion 52 and themicrostep drive controlling portion 53 to drive/control.

The inner circumferential position sensing portion 42 receives an outputsignal from the inner circumference switch 18, then senses that theoptical pickup 3 has been moved to a predetermined position on the innercircumference of the optical disk 1 when the inner circumference switch18 is turned ON, and then outputs a sensing signal to the moving timedeciding portion 43. At this time, the timer 41 counts a moving timerequired for moving the optical pickup 3 in the inner circumferentialdirection of the optical disk 1 in the full step drive and moving it toa predetermined position on the inner circumferential portion. Themoving time deciding portion 43 decides whether or not the moving timerequired to move the optical pickup 3 to the predetermined position onthe inner circumferential portion is within a predetermined time, basedon a moving time counted by the timer 41 and a sensing signal from theinner circumferential position sensing portion 42 indicating that amovement of the optical pickup 3 toward the predetermined position onthe inner circumferential portion has been completed.

In executing the full step drive control in the full step drivecontrolling portion 52, the full step driving current amplitude decidingportion 55 decides an amplitude value of the full step driving current.At this time, if the moving time deciding portion 43 decides that themoving time to move the optical pickup 3 to the predetermined positionon the inner circumferential portion exceeds the predetermined time, thefull step driving current amplitude deciding portion 55 increases theamplitude value of the full step driving current. The full step drivingcurrent profile generating portion 56 generates a current profile of thefull step driving current responding to the amplitude value decided bythe full step driving current amplitude deciding portion 55, and thenoutputs it to the stepping motor driving portion 14.

Translation data, which are used to translate the amplitude value of thefull step driving current to the supply time width of the drivingcurrent in the microstep drive mode when the moving time required tomove the optical pickup 3 to the predetermined position on the innercircumferential portion in the full step drive is within thepredetermined time, are stored in the full step driving currentamplitude-current supply time translation table 54. In executing themicrostep drive control in the microstep drive controlling portion 53,the microstep driving current supply time deciding portion 57 decides acurrent supply time of the microstep driving current in response to theamplitude value of the full step driving current, based on the output ofthe full step driving current amplitude-current supply time translationtable 54.

At this time, when the amplitude value of the full step driving currentis large, a supply time width of the driving current in the microstepdrive mode is set longer. The microstep driving current profilegenerating portion 58 generates a current profile of the microstepdriving current whose envelope is like a sinusoidal wave in answer tothe supply time width decided by the microstep driving current supplytime deciding portion 57, and outputs it to the stepping motor drivingportion 14.

Next, an operation of the optical disk device constructed as above willbe explained hereunder. Since the operations of reading/writing theinformation from/into the optical disk 1 are similar to those in thecommon optical disk device, their detailed explanation will be omittedherein. A controlling operation of the stepping motor 4 in the opticalaxis correction feeding operation in the microstep drive and arecalibrating operation using the full step drive in starting theoptical disk device, which are the operations peculiar to the presentembodiment, will be explained herein.

Upon reading/writing the information after the optical disk device isstarted or after the seek operation is finished, the optical axiscorrection feeding operation is executed. When the optical pickup 3starts reading of the information by turning ON the tracking servo, theactuator 6 is controlled such that the objective lens 5 is moved in theradial direction (from the inner circumference to the outercircumference or from the outer circumference to the innercircumference) to follow up the track of the optical disk 1. A lensshift, i.e., the objective lens 5 is shifted gradually from the centerof the base 7 of the optical pickup 3, is generated while theinformation is being read or written. After a predetermined amount oflens shift is generated, a driving current used in the microstep driveis applied from the stepping motor driving portion 14 to move thestepping motor 4 by a predetermined amount.

The base 7 of the optical pickup 3 is moved in the microstep drive ofthe stepping motor 4 to cancel the lens shift, and then the steppingmotor 4 is stopped. The above operations are executed successively untilthe objective lens 5 completes the reading of the final address of theoptical disk 1 or the final address of information reading intervaldesignated by the operator, and then the optical axis correction feedingoperation is finished when the objective lens 5 reaches the address.

Also, when the optical disk device is started, normally an ON state ofthe inner circumference switch 18 is checked by moving the opticalpickup 3 to a predetermined position of the inner circumferentialportion of the optical disk 1, then the recalibrating operation as anoperation to reset the optical pickup 3 to an initial position isexecuted, and then the reading or writing operation of the informationfrom or into the optical disk 1 is started.

In the third embodiment, the driving current control applied to drivethe stepping motor 4 during the optical axis correction feedingoperation in the microstep drive mode will be executed as follows. Inthis case, in the recalibrating operation, the amplitude value of thedriving current by which the movement toward the inner circumference indriving the stepping motor 4 in the full step drive mode can becompleted normally is calculated, and then a driving current supply timeduring the optical axis correction feeding operation in the microstepdrive mode is controlled in response to the amplitude value of thedriving current.

FIG. 7 is a flowchart showing procedures of the current supply timesetting operation in the microstep drive mode in the third embodiment.When the optical disk device is started, the driving current supply timesetting operation in the microstep drive mode is started (step S41), andthe recalibrating operation is executed. At this time, an innercircumference seek operation (inner circumference feeding operation) inthe full step drive is started (step S42). First, a counter n is set ton=1 as an initial value (step S43). Then, the full step driving currentamplitude deciding portion 55 sets a current amplitude value If(n) inperforming the full step drive to a reference value Ic (step S44).

Then, the full step driving current amplitude deciding portion 55 resetsthe timer 41 to zero (a count value T=0) (step S45). The full stepdriving current profile generating portion 56 generates a currentprofile of an amplitude value Ic to shift the optical pickup 3 towardthe inner circumferential side, and drives the stepping motor 4 via thestepping motor driving portion 14 and simultaneously starts the timer(step S46). The moving time deciding portion 43 decides whether or notthe inner circumference switch 18 has been turned ON after a lapse of apredetermined time, based on the sensing signal of the innercircumferential position sensing portion 42 and the count time countedby the timer 41 (step S47).

In step S47, if it is decided that the inner circumference switch 18 hasnot been turned ON after a lapse of the predetermined time, i.e., theoptical pickup 3 has not been moved to a predetermined position on theinner circumferential portion within a predetermined time, the full stepdriving current amplitude deciding portion 55 considered that the innercircumferential feed has not been executed normally because a load ofthe stepping motor 4 is increased, and then increments n to n=n+1 (stepS48). Then, the full step driving current amplitude deciding portion 55increases a current amplitude value If by α to get If(n+1)=If(n)+α (stepS49). Then, the process goes back to step S45. The timer 41 is reset andthe inner circumference seek operation in the full step drive mode isexecuted again. The operations in steps S45 to S49 are repeated untilthe inner circumference switch 18 has been turned ON within thepredetermined time and the movement of the optical pickup 3 to thepredetermined position on the inner circumferential portion has beencompleted.

FIG. 8 is a view showing a full step drive current of a stepping motorin inner circumference seek operation in the third embodiment. As shownin FIG. 8, when the movement of the optical pickup 3 to thepredetermined position on the inner circumferential portion has not beencompleted within the predetermined time, the inner circumferentialfeeding operation is carried out again while increasing the amplitudevalue of the driving current by α stepwise.

In contrast, in step S47, if it is decided that the inner circumferenceswitch 18 has been turned ON within the predetermined time, i.e., if themovement of the optical pickup 3 to the predetermined position on theinner circumferential portion has been completed within thepredetermined time, the inner circumference seek operation is ended(step S50).

Then, in order to decide the current supply time width of the drivingcurrent in the microstep drive, the microstep driving current supplytime deciding portion 57 outputs the conversion coefficient kcorresponding to the current amplitude value If by using the full stepdriving current amplitude-current supply time translation table 54 (stepS51). Then, the microstep driving current supply time deciding portion57 sets a current supply time tm obtained by multiplying the currentsupply time tc as the reference at an ordinary temperature by theconversion coefficient k to the supply time width of the driving current(step S52). Then, the driving current supply time setting operation inthe microstep drive mode is ended (step S53).

FIG. 9 are views showing the driving current in the microstep drive modeof the stepping motor in the third embodiment respectively. When thenormal operation current amplitude value If in the full step drive modeis lower than the reference value Ic, i.e., when the load of thestepping motor is smaller than a predetermined level, e.g., theconversion coefficient k=1 is set, the supply time width of the drivingcurrent is set to the current supply time t as the reference at anordinary temperature, as shown in FIG. 9( a), and the pulse drivingcurrent whose envelope is like a sinusoidal wave is supplied from thestepping motor driving portion 14. When the normal operation currentamplitude value If in the full step drive mode is higher than thereference value Ic, i.e., when the load of the stepping motor is largerthan a predetermined level, e.g., the conversion coefficient k>1 is set,the supply time width of the driving current is set to the currentsupply time tm=k×tc, as shown in FIG. 9( b), and the driving current isswitched such that the supply time width is prolonged.

At this time, the supply time width of the driving current can bechanged continuously or stepwise in response to the current amplitudevalue If. Here, the conversion coefficient k may be set in response tothe moving time required until the inner circumferential seek operationis normally completed by using a predetermined current amplitude value,in place of the current amplitude value If. Also, an increment value ofthe current amplitude value in the full step drive mode is not limitedto a constant value α but such increment value may be changed inresponse to the number of increase or may be changed every recalibratingoperation. Alternately, such increment value may be changed according tothe ambient temperature by providing a temperature sensor to the insideof the equipment, or the like. Also, the driving current supply time inthe microstep drive mode can be set based on the current amplitude valueas well as ambient temperature information supplied from the temperaturesensor provided to the inside of the equipment.

In this manner, in the third embodiment, in the recalibrating operationexecuted in starting the equipment, the load state is estimated based onwhether or not the optical pickup is moved to the inner circumferentialposition by changing the current amplitude value of the driving currentin the full step drive mode and the normal operation can be done there.The current amplitude value by which the inner circumferential feedingoperation is completed normally within the predetermined time isderived, then the conversion coefficient is calculated in response tothis current amplitude value, and then the current supply timeresponding a magnitude (i.e., load of the stepping motor in the normaloperation) of the current amplitude value is set by multiplying thecurrent supply time as the reference by the conversion coefficient.Therefore, the current supply time of the driving current in themicrostep drive mode is changed. At this time, when the currentamplitude value is large, the supply time width of the driving currentis set longer. As a result, upon executing the optical axis correctionfeeding operation when the lens shift of the objective lens exceeds apredetermined amount, the stepping motor can be driven by the adequatetorque in the broad temperature environment.

As explained above, according to the third embodiment, in executing theoptical axis correction feeding operation in the microstep drive, whenthe driving current is supplied intermittently every predetermined timewidth by suppressing a consumption current to reduce an amount of heatgeneration, the current amplitude value of the driving current thatallows the feeding operation of the optical pickup normally in the fullstep drive is sensed, and then the current supply time width in themicrostep drive mode is set in response to the sensed current amplitudevalue. Therefore, the stepping motor can be driven by the torque thatcorresponds to the load torque in operation. As a result, in the opticalpickup driving mechanism using the stepping motor, the feeding operationof the optical pickup can be stabilized even in the broad operatingtemperature environment.

FIG. 10 is a block diagram showing a schematic configuration of anoptical disk device according to a fourth embodiment of the presentinvention. Here the same reference symbols are affixed to the sameconstituent elements as those in the above first to third embodiments,and their explanation will be omitted herein.

An optical disk device of the fourth embodiment includes the innercircumference switch 18 that is turned ON when the optical pickup 3arrives at a predetermined position of the inner circumferential portionof the optical disk 1. Also, the optical disk device includes acontroller 60 is constructed to have the spindle motor controllingportion 21, the optical pickup controlling portion 22, the lens shiftamount sensing portion 24, the timer 41, the inner circumferentialposition sensing portion 42, the moving time deciding portion 43, and astepping motor controlling portion 61. The stepping motor controllingportion 61 is constructed to have a full step drive controlling portion62, a microstep drive controlling portion 63, and a full step drivingcurrent pulse rate-current supply time translation table 64. The fullstep drive controlling portion 62 has a full step driving current pulserate deciding portion 65 and a full step driving current profilegenerating portion 66. The microstep drive controlling portion 63 has amicrostep driving current supply time deciding portion 67, and amicrostep driving current profile generating portion 68.

In the above configuration, the optical pickup controlling portion 22 inthe controller 60 outputs a control signal, which is applied to controla position of the objective lens 5 based on the focus error signal andthe tracking error signal output from the head amplifier 15, to theoptical pickup driving portion 13. The focus actuator and the trackingactuator of the optical pickup 3 are driven by the optical pickupdriving portion 13 based on this control signal. The lens shift amountsensing portion 24 senses an amount of shift at which the objective lens5 shifts from the center of the base 7 of the optical pickup 3.

The feed screw 10 serves as the output shaft of the stepping motor 4.The rotating power of the stepping motor 4, when it rotates, istransmitted from the feed screw 10 via the feed screw holder 11, so thatthe base 7 of the optical pickup 3 is moved in the radial direction ofthe optical disk 1. Normally, in the optical disk device, the seekoperation to read the information about inner and outer circumferencesof the optical disk must be executed frequently. Therefore, the greaseis smeared on the feed screw 10 and the feed screw holder 11 to secure awear resistance of the sliding portions.

The stepping motor 4 is rotated by the driving current fed from thestepping motor driving portion 14. The stepping motor controllingportion 61 in the controller 60 controls the driving current output fromthe stepping motor driving portion 14, and can switch the full stepdrive and the microstep drive by the full step drive controlling portion62 and the microstep drive controlling portion 63 to drive/control.

The inner circumferential position sensing portion 42 receives theoutput signal from the inner circumference switch 18, then senses thatthe optical pickup 3 has been moved to a predetermined position on theinner circumference of the optical disk 1 when the inner circumferenceswitch 18 is turned ON, and then outputs the sensing signal to themoving time deciding portion 43. At this time, the timer 41 counts amoving time required for moving the optical pickup 3 in the innercircumferential direction of the optical disk 1 in the full step driveand moving it to a predetermined position on the inner circumferentialportion. The moving time deciding portion 43 decides whether or not themoving time required to move the optical pickup 3 to the predeterminedposition on the inner circumferential portion is within a predeterminedtime, based on a moving time counted by the timer 41 and a sensingsignal from the inner circumferential position sensing portion 42indicating that a movement of the optical pickup 3 toward thepredetermined position on the inner circumferential portion has beencompleted.

In executing the full step drive control in the full step drivecontrolling portion 62, the full step driving current pulse ratedeciding portion 65 decides a pulse rate of the full step drivingcurrent. At this time, if the moving time deciding portion 43 decidesthat the moving time to move the optical pickup 3 to the predeterminedposition on the inner circumferential portion exceeds the predeterminedtime, the full step driving current pulse rate deciding portion 65decreases the pulse rate of the full step driving current. The full stepdriving current profile generating portion 66 generates a currentprofile of the full step driving current responding to the pulse ratedecided by the full step driving current pulse rate deciding portion 65,and then outputs it to the stepping motor driving portion 14.

Translation data, which are used to translate the pulse rate of the fullstep driving current to the supply time width of the driving current inthe microstep drive mode when the moving time required to move theoptical pickup 3 to the predetermined position on the innercircumferential portion in the full step drive is within thepredetermined time, are stored in the full step driving current pulserate-current supply time translation table 64. In executing themicrostep drive control in the microstep drive controlling portion 63,the microstep driving current supply time deciding portion 67 decides acurrent supply time of the microstep driving current in response to thepulse rate of the full step driving current, based on the output of thefull step driving current pulse rate-current supply time translationtable 64. At this time, when the pulse rate of the full step drivingcurrent is small, a supply time width of the driving current in themicrostep drive mode is set longer. The microstep driving currentprofile generating portion 68 generates a current profile of themicrostep driving current whose envelope is like a sinusoidal wave inresponse to the supply time width decided by the microstep drivingcurrent supply time deciding portion 67, and outputs it to the steppingmotor driving portion 14.

Next, an operation of the optical disk device constructed as above willbe explained hereunder. Since the operations of reading/writing theinformation from/into the optical disk 1 are similar to those in thecommon optical disk device, their detailed explanation will be omittedherein. A controlling operation of the stepping motor 4 in the opticalaxis correction feeding operation in the microstep drive and arecalibrating operation using the full step drive in starting theoptical disk device, which are the operations peculiar to the presentembodiment, will be explained herein.

Upon reading/writing the information after the optical disk device isstarted or after the seek operation is finished, the optical axiscorrection feeding operation is executed. When the optical pickup 3starts reading of the information by turning ON the tracking servo, theactuator 6 is controlled such that the objective lens 5 is moved in theradial direction (from the inner circumference to the outercircumference or from the outer circumference to the innercircumference) to follow up the track of the optical disk 1. A lensshift, i.e., the objective lens 5 is shifted gradually from the centerof the base 7 of the optical pickup 3, is generated while theinformation is being read or written. After a predetermined amount oflens shift is generated, a driving current used in the microstep driveis applied from the stepping motor driving portion 14 to move thestepping motor 4 by a predetermined amount.

The base 7 of the optical pickup 3 is moved in the microstep drive ofthe stepping motor 4 to cancel the lens shift, and then the steppingmotor 4 is stopped. The above operations are executed successively untilthe objective lens 5 completes the reading of the final address of theoptical disk 1 or the final address of information reading intervaldesignated by the operator, and then the optical axis correction feedingoperation is finished when the objective lens 5 reaches the address.

Also, when the optical disk device is started, normally an ON state ofthe inner circumference switch 18 is checked by moving the opticalpickup 3 to a predetermined position of the inner circumferentialportion of the optical disk 1, then the recalibrating operation as anoperation to reset the optical pickup 3 to an initial position isexecuted, and then the reading or writing operation of the informationfrom or into the optical disk 1 is started.

In the fourth embodiment, the driving current control applied to drivethe stepping motor 4 during the optical axis correction feedingoperation in the microstep drive mode will be executed as follows. Inthis case, in the recalibrating operation, the pulse rate of the drivingcurrent by which the movement toward the inner circumference in drivingthe stepping motor 4 in the full step drive mode can be completednormally is calculated, and then a driving current supply time duringthe optical axis correction feeding operation in the microstep drivemode is controlled in response to the pulse rate of the driving current.

FIG. 11 is a flowchart showing procedures of the current supply timesetting operation in a microstep drive mode in the fourth embodiment.When the optical disk device is started, a driving current supply timesetting operation in the microstep drive mode is started (step S61), andthe recalibrating operation is executed. At this time, the innercircumference seek operation in the full step drive (inner circumferencefeeding operation) is started (step S62). First, a counter n is set ton=1 as an initial value (step S63). Then, the full step driving currentpulse rate deciding portion 65 sets a pulse rate Pf(n) in the full stepdrive mode to a reference value Pc (step S64).

Then, the full step driving current pulse rate deciding portion 65resets the timer 41 to zero (count value T=0) (step S65). The full stepdriving current profile generating portion 66 generates a currentprofile of a pulse rate Pc to shift the optical pickup 3 toward theinner circumferential side, and drives the stepping motor 4 via thestepping motor driving portion 14 and simultaneously starts the timer(step S66). The moving time deciding portion 43 decides whether or notthe inner circumference switch 18 has been turned ON after a lapse of apredetermined time, based on the sensing signal of the innercircumferential position sensing portion 42 and the count time countedby the timer 41 (step S67).

FIG. 12 are views showing a relationship between a pulse rate of adriving current of a stepping motor and a torque in the fourthembodiment respectively. FIG. 12( a) shows the case where the innercircumferential seek operation can be done at a pulse rate Pc as areference value within a predetermined time because the load torque issmall, and FIG. 12( b) shows the case where the inner circumferentialseek operation cannot be completed at a pulse rate Pc as a referencevalue within a predetermined time because the load torque is large.

In step S67, if it is decided that the inner circumference switch 18 hasnot been turned ON after a lapse of the predetermined time, i.e., theoptical pickup 3 has not been moved to a predetermined position on theinner circumferential portion within a predetermined time, the full stepdriving current pulse rate deciding portion 65 considered that the innercircumferential feed has not been executed normally because a load ofthe stepping motor 4 is increased. In this case, it is decided that theinner circumferential feed has not been executed normally because theload torque is larger than the torque generated by the motor ((1) ofFIG. 12( b)) and an out-of-step phenomenon occurs, and then theincrement value n is increased by one to n=n+1 (step S68). Then, thefull step driving current pulse rate deciding portion 65 decreases apulse rate Pf by one step α to get Pf(n+1)=Pf(n)+α (step S69). Then, theprocess goes back to step S65. The timer 41 is reset and the innercircumference seek operation in the full step drive mode is executedagain ((2) of FIG. 12( b)). The operations in steps S65 to S69 arerepeated until the inner circumference switch 18 has been turned ONwithin the predetermined time and the movement of the optical pickup 3to the predetermined position on the inner circumferential portion hasbeen completed.

FIG. 13 is a view showing the full step drive current of the steppingmotor in inner circumference seek operation in the fourth embodiment. Asshown in FIG. 13, when the movement of the optical pickup 3 to thepredetermined position on the inner circumferential portion has not beencompleted within the predetermined time, the inner circumferentialfeeding operation is carried out again while decreasing the pulse rateof the driving current by α stepwise.

In contrast, in step S67, if it is decided that the inner circumferenceswitch 18 has been turned ON within the predetermined time, i.e., if themovement of the optical pickup 3 to the predetermined position on theinner circumferential portion has been completed within thepredetermined time, the inner circumference seek operation is finished(step S70). At this time, the load torque is smaller than the torquegenerated by the motor ((3) of FIG. 12( b)), and the normal operationcan be executed.

Then, in order to decide the current supply time width of the drivingcurrent in the microstep drive, the microstep driving current supplytime deciding portion 67 outputs the conversion coefficient kcorresponding to the pulse rate Pf by using the full step drivingcurrent pulse rate-current supply time translation table 64 (step S71).Then, the microstep driving current supply time deciding portion 67 setsa current supply time tm obtained by multiplying the current supply timetc as the reference at an ordinary temperature by the conversioncoefficient k to the supply time width of the driving current (stepS72). Then, the driving current supply time setting operation in themicrostep drive mode is ended (step S73).

FIG. 14 are views showing the driving current in the microstep drivemode of the stepping motor in the fourth embodiment respectively. Whenthe normal operation pulse rate Pf in the full step drive mode is lowerthan the reference value Pc, i.e., when the load of the stepping motoris smaller than a predetermined level, e.g., the conversion coefficientk=1 is set, the supply time width of the driving current is set to thecurrent supply time t as the reference at an ordinary temperature, asshown in FIG. 14( a), and the pulse driving current whose envelope islike a sinusoidal wave is supplied from the stepping motor drivingportion 14. When the normal operation pulse rate Pf in the full stepdrive mode is smaller than the reference value Pc, i.e., when the loadof the stepping motor is larger than a predetermined level, e.g., theconversion coefficient k>1 is set, the supply time width of the drivingcurrent is set to the current supply time tm=k×tc, as shown in FIG. 14(b), and the driving current is switched such that the supply time widthis prolonged. At this time, the supply time width of the driving currentcan be changed continuously or stepwise in response to the pulse ratePf.

Here, the conversion coefficient k may be set in response to the movingtime required until the inner circumferential seek operation is normallycompleted by using a predetermined current amplitude value, in place ofthe pulse rate Pf. Also, a decrement value of the pulse rate in the fullstep drive mode is not limited to a constant value α but such decrementvalue may be changed in response to the number of decrease or may bechanged every recalibrating operation. Alternately, such increment valuemay be changed according to the ambient temperature by providing atemperature sensor to the inside of the equipment, or the like. Also,the driving current supply time in the microstep drive mode can be setbased on the pulse rate as well as ambient temperature informationsupplied from the temperature sensor provided to the inside of theequipment.

In this manner, in the fourth embodiment, in the recalibrating operationexecuted in starting the equipment, the load state is estimated based onwhether or not the optical pickup is moved to the inner circumferentialposition by changing the pulse rate of the driving current in the fullstep drive mode and the normal operation can be done there. The pulserate by which the inner circumferential feeding operation is completednormally within the predetermined time is derived, then the conversioncoefficient is calculated in response to this pulse rate, and then thecurrent supply time responding a magnitude (i.e., load of the steppingmotor in the normal operation) of the pulse rate is set by multiplyingthe current supply time as the reference by the conversion coefficient.Therefore, the current supply time of the driving current in themicrostep drive mode is changed. At this time, when the pulse rate issmall, the supply time width of the driving current is set longer. As aresult, upon executing the optical axis correction feeding operationwhen the lens shift of the objective lens exceeds a predeterminedamount, the stepping motor can be driven by the adequate torque in thebroad temperature environment.

As explained above, according to the fourth embodiment, in executing theoptical axis correction feeding operation in the microstep drive, whenthe driving current is supplied intermittently every predetermined timewidth by suppressing a consumption current to reduce an amount of heatgeneration, the current amplitude value of the driving current thatallows the feeding operation of the optical pickup normally in the fullstep drive is sensed, and then the current supply time width in themicrostep drive mode is set in response to the sensed pulse rate.Therefore, the stepping motor can be driven by the torque thatcorresponds to the load torque in operation. As a result, in the opticalpickup driving mechanism using the stepping motor, the feeding operationof the optical pickup can be stabilized even in the broad operatingtemperature environment.

As a consequence, according to the above first to fourth embodiments,even in the broad operation temperature range such as the onboardapplication, or the like, occurrence of the feeding operation failure bythe influence of the load variation due to a grease viscosity can beprevented and also the reading/writing of information can be carried outprecisely. Therefore, the optical disk device can be operated stably inthe broad temperature environment. Also, the stability and thereliability of the optical disk device can be enhanced by applying theabove optical pickup feed controlling method to the optical disk device.In addition, when the above optical disk device is applied to theonboard equipment, such optical disk device can be operated normallyeven in such a condition that the vehicle is used in the broadtemperature environment.

The present invention is explained in detail with reference toparticular embodiments. But it is apparent for those skilled in the artthat various variations and modifications can be applied withoutdeparting from a spirit and a scope of the present invention.

This application is based upon Japanese Patent Application (PatentApplication No. 2004-163221) filed on Jun. 1, 2004, Japanese PatentApplication (Patent Application No. 2004-163222) filed on Jun. 1, 2004,and Japanese Patent Application (Patent Application No. 2004-163223)filed on Jun. 1, 2004; the contents of which are incorporated herein byreference.

INDUSTRIAL APPLICABILITY

The present invention possesses such an advantage that the feedingoperation of the optical pickup can be stabilized in the optical pickupdriving mechanism using the stepping motor even in the broad operatingtemperature environment, and is useful to the optical disk device havingthe optical pickup for executing at least one of reading and writingoperations of the information from and into the disk-type opticalrecording medium, and the like.

1. An optical disk device, comprising: an optical pickup that readsinformation recorded on an optical disk; a stepping motor that moves theoptical pickup in a radial direction of the optical disk; a drivingcurrent supplying unit that supplies a driving current to drive thestepping motor, and executes selectively a full step drive and amicrostep drive; a full step drive deciding unit that decides whether ornot an operation performed when the optical pickup is moved in the fullstep drive is normally ended; a drive controlling unit that executesdrive control of the stepping motor by changing the driving currentapplied in the microstep drive in response to a decision result; anoptical pickup position sensing unit that senses whether or not amovement of the optical pickup to a predetermined position of an innercircumference of the optical disk is completed; and a moving timedeciding unit that decides a moving time required until the opticalpickup is moved to the predetermined position of the inner circumferencein the full step drive, wherein the driving current supplying unitsupplies an intermittent driving current at a predetermined time widthto the stepping motor in executing the microstep drive; and wherein thedrive controlling unit changes a supply time width of the drivingcurrent in response to the moving time of the optical pickup.
 2. Theoptical disk device according to claim 1, wherein the drive controllingunit changes the supply time width of the driving current into anincreased value when the moving time is equal to or greater than apredetermined value.
 3. An optical disk device according to claim 1,wherein a decision regarding a drive of the optical pickup in the fullstep drive is performed during an inner circumferential feedingoperation which is applied to initialize a position of the opticalpickup immediately after the optical disk device is started.